1. Field of the Invention
This invention relates to a process for selectively sulfamating primary organic amines. More particularly, it relates to a two-step primary amine sulfamation process employing catechol sulfate.
2. The Prior Art
Over the years, many methods have evolved for sulfonation of primary amines. Interest in the cyclamate class of nonnutritive sweeteners and in heparin and analogs as anticoagulants has been largely responsible for the development of synthetic methods of sulfamic acid salt preparation. Methods in current use include (1) sulfonation of amines with chlorosulfonic acid: see (Gilbert, E. E., "Sulfonation and Related Reactions"; Interscience: New York, 1965; Chapter 7 and references therein); (see Bieber, T., Amer. Chem. Soc., 1953, 75, 1405); (see Bieber, T., J. Amer. Chem. Soc., 1953, 75, 1409); (See Weiss, G., Schulze, G., Ann., 1969, 729, 40). While these methods have utility with simple amine group- or amine-precursor-containing materials, they present the problem of being nonselective when other functionalities such as hydroxyls and the like are present and thus lead to poor yields of desired sulfonate products.
For example, while studying the dihydrochalcone class of nonnutritive sweeteners, we wished to prepare intensely sweet sulfamoethyl dihydrochalcone 1. ##STR1## Synthesis of 1 via sulfonation of the corresponding amine with Me.sub.3 N.SO.sub.3, the mildest of the commonly employed N-sulfonating agents, was plagued by an inability to achieve selective N-sulfonation and problems in removal of the foul-smelling Me.sub.3 N after conversion of the intermediate trimethylammonium salt to the potassium salt. The product thus obtained required preparative HPLC purification and was obtained in only 15-20% yield.
Clearly, a selective method of amine sulfamation is needed which is compatible with labile functionality such as is present in 1.
Compound 1 and its precursors are the subject of United States Patent application Ser. No. 140,064, filed of even date herewith and incorporated by reference herein.